Diffusion coefficients of the ternary system (2-hydroxypropyl-β-cyclodextrin plus caffeine plus water) at T=298.15 K

Ternary mutual diffusion coefficients measured by Taylor dispersion method (D-11, D-22, D-12, and D-21) are reported for aqueous solutions of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) +caffeine at T = 298.15 K at carrier concentrations from (0.000 to 0.010) mol . dm(-3), for each solute. respectively. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and thermodynamic behaviour of caffeine and 2-hydroxypropyl-beta-cyclodextrin in solution. For example, from these data it will be possible to estimate some parameters, such as the fraction of associated species HP-beta-CD (X-1) and caffeine (X-2) in this complex, the monomer and dimer fractions, X-2(M) and X-2(D), respectively, and the limiting diffusion coefficients of the HP-beta-CD, D-HPBCD(o), of the climers caffeine entities, D-D(o), and of those complexes (1:1). D-complex(o). (C) 2009 Elsevier Ltd. All rights reserved.